Physiology 2130 Lecture Notes - Lecture 8: Aortic Valve, Heart Valve, Pacemaker Potential
8 Dec 2016
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Module #8 circulatory system i: the heart (sections 8. 1 to 8. 41) The two principal types of myocardial cells: contractile cells and nodal/conducting cells. Contractile cells are consider to be the real muscle cells of the heart and form most of the walls of the atria and ventricles. They contain small contractile proteins actin and myosin arranged in bundles of myofibrils surrounded by a sarcoplasmic reticulum. They have only one uncles and many mitochondria. These cells are extremely efficient at extracting oxygen about 2x the amount of other cells. The cells are shorter, branched, and joined together by special structures intercalated discs. These structures contain tight junctions that bind the cells together, while gap junctions allow for movement of ions and ion currents. Because of the gap junctions, the myocardial cells can conduct aps w/o need for nerves. Nodal/conducting cells contract very weakly because they contain very few contractile elements (myofibrils).
